Geocoding amp; Data Collection with GPS课件.ppt

How GPS Works GPS receivers collect the signals transmitted from more than 24 satellites—21 active satellites and three spares. The system is called NAVSTAR, and is maintained by the U.S. Department of Defense The satellites are circling the earth in six orbital planes at an altitude of approximately 20,000 km. At any given time five to eight GPS satellites are within the “field of view” of a user on the earth’s surface The position on the earth’s surface is determined by measuring the distance from several satellites Notes to explain why we need three satellites to indentify a location. The GC classification can be created through digitizing and placement of coded units that fit with the boundaries of a geographic area for a given country Geocoding Data Collection with GPS Summary Introduction to Geocoding Geocoding: Concepts and Definitions Relationship to other Census Processes Approaches to Data Collection NSO Benefits Concluding Remarks Introduction to GPS How GPS Works Sources of Error Accuracy Selecting a GPS Advantages Disadvantages Introduction Many NSOs have a specialized coding scheme and understand geocoding as a dynamic process Clarification within the statistical community Expansion and discussion on components and methods within the process of geocoding The purpose of this section is to introduce geocoding concepts relevant for census mapping and the different approaches to related data collection. Geocoding Definitions: Conceptual/Operational Geocoding vs Georeferencing Census Hierarchies Coding Scheme Data Collection Methods Direct Collection Matching Approach Benefits for NSOs “Geocoding can be broadly defined as the assignment of a code to a geographic location. Usually however, Geocoding refers to a more specific assignment of geographic coordinates (latitude, longitude) to an individual address.” Reference: UN Report of the Expert Group Meeting on Contemporary Practices in Census Mapping and Use of Geographical Information S